Antimicrobials in Higher Plants: classification, mode of action and bioactivities

By Ishwar Singh Plants produce an enormous number of phytochemicals as a part of their primary as well as secondary metabolism of those many could be of therapeutic value especially antimicrobial application to human beings. Majority of the isolated antimicrobials pertain to chemical groups namely, phenolics, terpenes, alkaloids and polypeptides, and exhibit multiple mechanisms of action against disease causing microorganisms. The target site varies amongst different antimicrobials ranging from molecular level to organism level of organization. During their antimicrobial action at molecular level these phytochemicals interact covalently and non-covalently with macromolecules and render them non-functional. At cellular level antimicrobials disrupt the functioning of various cell components such as capsule, cell wall, cell membrane and mitochondria leading to the death of pathogens. Various antimicrobial activities like antiviral, antibacterial and antifungal activities of different plants and their isolated chemicals have also been discussed.